The present invention relates generally to catheters for performing medical procedures. More particularly, the present invention relates to methods of fabricating catheter shafts.
Intravascular catheters are currently utilized in a wide variety of minimally-invasive medical procedures. Generally, an intravascular catheter enables a physician to remotely perform a medical procedure by inserting the catheter into the vascular system of the patient at an easily accessible location and navigating the tip of the catheter to the desired target site. By this method, virtually any target site in the patient""s vascular system may be remotely accessed, including the coronary, cerebral, and peripheral vasculature.
Typically, the catheter enters the patient""s vasculature at a convenient location such as a blood vessel in the neck or near the groin. Once the distal portion of the catheter has entered the patient""s vascular system the physician may urge the distal tip forward by applying longitudinal forces to the proximal portion of the catheter. For the catheter to effectively communicate these longitudinal forces it is desirable that the catheter have a high level of pushability and kink resistance particularly near the proximal end.
Frequently the path taken by a catheter through the vascular system is tortuous, requiring the catheter to change direction frequently. In some cases, it may even be necessary for the catheter to double back on itself. In order for the catheter to conform to a patient""s tortuous vascular system, it is desirable that intravascular catheters be very flexible, particularly near the distal end.
While advancing the catheter through the tortuous path of the patients vasculature, physicians often apply torsional forces to the proximal portion of the catheter to aid in steering the catheter. To facilitate the steering process, the distal portion of the catheter may include a plurality of bends or curves. Torsional forces applied on the proximal end must translate to the distal end to aid in steering. It is therefore desirable that the proximal portion of an intravascular catheter have a relatively high level of torquability to facilitate steering.
After the intravascular catheter has been navigated through the patient""s vascular system so that its distal end is adjacent the target site, the catheter may be used for various diagnostic and/or therapeutic purposes. One example of a diagnostic use for an intravascular catheter is the delivery of radiopaque contrast solution to enhance fluoroscopic visualization. In this application, the intravascular catheter provides a fluid path leading from a location outside the body to a desired location inside the body of a patient. In order to maintain a fluid path, it is desirable that intravascular catheters be sufficiently resistant to kinking. In addition, because such fluids are delivered under pressure, it is also desirable that intravascular catheters be sufficiently resistant to bursting or leaking.
Examples of therapeutic purposes for intravascular catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These angioplasty techniques typically involve the use of a guide catheter and a balloon catheter. During these procedures, the distal end of the guide catheter is typically inserted into the femoral artery located near the groin of the patient. The guide catheter is urged through the vasculature of the patient until its distal end is proximate the restriction. In many cases, the distal end of the guide catheter is positioned in the ostium of the coronary artery. The balloon catheter may then be fed through a lumen in the guide catheter such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. In this application, it is desirable that the guide catheter provide a low friction path for the balloon catheter. The balloon is inflated by urging a liquid though the elongate shaft of the balloon catheter and into the balloon. In this application, the balloon catheter must provide an unobstructed path for the inflation fluid. It is also desirable that the catheter be substantially free of leaks.
As described at length above, it is desirable to combine a number of performance features in an intravascular catheter. It is desirable that the catheter have a relatively high level of pushability and torqueability, particularly near its proximal end. It is also desirable that a catheter be relatively flexible, particularly near it""s distal end. The need for this combination of performance features is often addressed by building a catheter which has two or more discrete tubular members having different performance characteristics. For example, a relatively flexible distal section may be spliced to a relatively rigid proximal section. When a catheter is formed from two or more discrete tubular members, it is often necessary to form a bond between the distal end of one tubular member and the proximal end of another tubular member.
Intravascular catheters are often used in conjunction with a guidewire. When this is the case, the guidewire may be advanced through the patient""s vasculature until its distal tip has reached a desired target location. Once the distal portion of the guidewire is proximate the desired location, the catheter may be threaded onto the guidewire and urged distally until the distal end of the catheter is proximate the target location.
Intravascular catheters adapted for use with a guidewire typically fall into one of two categories: the over-the-wire category or the single operator exchange (SOE) category. An over-the wire type of catheter includes a guidewire lumen extending from the distal tip of the catheter to the proximal end of the catheter. Whereas, a single operator exchange catheter typically includes a relatively short guidewire lumen proximate the distal end of the catheter.
Single operator exchange catheters were developed in response to difficulties encountered when exchanging over-the-wire catheters. Generally, it is desirable to leave the guidewire in place while a first catheter is withdrawn from the patient and replaced with a second catheter. Maintaining the position of the guidewire tip during the procedure aids the physician in quickly positioning the distal end of the second catheter proximate the target area.
In order to keep the guidewire tip near the target area, the guidewire must be held in place throughout the catheter exchange procedure. A portion of the guidewire is typically grasped by the physician in order to withdraw the first catheter while maintaining distal end of the guidewire in the desired position. To properly anchor the guidewire, a portion of the guidewire must be exposed at all times so it is available for the physician to grasp. In the case of an over-the-wire catheter, this requires that the length of the guidewire extending beyond the patient""s body be longer than the catheters. In some cases, length must be added to the guidewire using a guidewire extension. In many cases intravascular catheters are longer than 200 cm. Correspondingly, there may be more than 200 cm of wire extending from the patient. Managing this length of wire during a catheter exchange procedure is awkward, and typically requires two persons. In particular, contamination must be avoided by assuring that the guidewire is not dropped from the sterile field.
An SOE catheter, on the other hand, has a relatively short guidewire wire lumen proximate its distal tip. The length of guidewire extending beyond the body of the patient need only be slightly longer than the guidewire lumen of the catheter. The physician may anchor or hold the guidewire as the first catheter is removed from the body with the exchange occurring over the shorter guidewire lumen. The guidewire lumen of an SOE catheter typically includes a distal guidewire port disposed at the distal tip of the catheter and a proximal guidewire port disposed proximally of the distal end of the catheter. It is desirable to fabricate an SOE catheter, to include a proximal guidewire port, while maintaining the other desirable performance features described previously.
The present invention relates generally to catheters for performing medical procedures. More particularly, the present invention relates to catheters having a shaft including one or more elongate support members. An elongate support member in accordance with one embodiment of the present invention comprises a first flange, a second flange, and a central member extending between the first flange and the second flange. The first flange and the second flange define an elongate channel having an elongate opening. An inflation conduit defining an inflation lumen is disposed in elongate channel. During the assembly of proximal shaft portion, the inflation conduit may be passed through elongate opening and laid in the elongate channel. In a preferred embodiment, a sheath is disposed about the elongate support member and the inflation conduit. Also in a preferred embodiment, the first flange and the second flange of the elongate support member each have a free end proximate the elongate opening of the elongate channel and a fixed end which is fixed to the central member of the elongate support member.
In a preferred embodiment, the elongate support member is comprised of a metal such as stainless steel, nickel titanium alloys, other alloys, etc. Also in a preferred embodiment, the elongate support member may absorb the energy of bending through deformation of the first flange and the second flange. In a particularly preferred embodiment, the free end of the first flange is free to move relative to the free end of the second flange. Bending energy applied to the elongate support member may be absorbed as the free end of the first flange and the free end of the second flange move relative to one another. The ability of the elongate support member to absorb bending energy may enhance the kink resistance, fracture resistance, and/or toughness of a catheter including the elongate support member.
The elongate support member, preferably, includes a right portion comprising one or more flanges extending beyond a right side of a first central plane extending through a longitudinal axis of the elongate support member and a left portion comprising one or more flanges extending beyond a left side of the first central plane. Additionally, the elongate support member includes a ventral portion comprising one or more flanges extending beyond a ventral side of a second central plane extending through a longitudinal axis of the elongate support member and a dorsal portion comprising one or more flanges extending beyond a dorsal side of the second central plane.
In a preferred embodiment, the right portion has a transverse cross sectional area which is substantially equal to a transverse cross sectional area of the left portion. Also in a preferred embodiment, the ventral portion has a transverse cross sectional area which is substantially equal to a transverse cross sectional area of the dorsal portion. In a particularly preferred embodiment, the transverse cross sectional area the ventral portion, the transverse cross sectional area the dorsal portion, the transverse cross sectional area the right portion, and the transverse cross sectional area the left portion are all substantially equal.
In a preferred embodiment, the elongate support member resists bending along the first central plane. Also in a preferred embodiment, the elongate support member resists bending along the second central plane. In a particularly preferred embodiment, the resistance of the elongate support member to bending along second central plane is substantially equal to it""s resistance to bending along first central plane. The non-preferential resistance to bending of the elongate support member may enhance the pushability and kink resistance of a catheter including the elongate support member.